1. Field of the Invention
The present invention relates to a method and an apparatus for polishing a substrate using a polishing pad and slurry. More particularly, the present invention relates to the washing of the polishing pad to remove slurry and other particles therefrom.
2. Description of the Related Art
Recently, the semiconductor industry has made great strides as the use of information media including computers has increased. As concerns its function, a semiconductor device must operate at a high speed and have a large data storage capacity. Accordingly, improvements in semiconductor manufacturing techniques have centered around increasing the degree of integration, reliance and response speed of semiconductor devices.
Chemical mechanical polishing (CMP) was developed in the 1980s for increasing the degree of integration of semiconductor devices. CMP is a manufacturing technique for polishing a surface on a substrate to attain a high degree of surface flatness. Examples of CMP polishing technologies are disclosed in U.S. Pat. No. 5,709,593 issued to Guthrie et al., and in U.S. Pat. No. 6,051,499 issued to Tolles et al. FIG. 1 illustrates the polishing of a surface on a substrate 10 using a conventional a polishing apparatus.
Referring to FIG. 1, the substrate 10 is grasped by a carrier head 12 which can simultaneously rotate and oscillate. The substrate 10 is pressed by the carrier head 12 against a rotatable polishing pad 14 mounted on a platen 13. In this state, the substrate 10 is polished by slurry 16 which is sprayed onto the polishing pad 14. More specifically, the substrate 10 is polished mechanically by an abrasive component of the slurry 16 and the abrasive surface of polishing pad 14, and the substrate 10 is polished chemically by a chemical component the slurry 16.
In this polishing process, particles generated by the polishing process and some of the slurry remain on the polishing pad 14. If these particles and slurry were to remain on the polishing pad, they could cause a defect to occur on a substrate as it is being polished. Therefore, the particles and slurry are removed from the polishing pad 14 while the substrate 10 is being polished.
FIG. 2 shows a washing device 20 for washing a polishing pad 14 of the conventional polishing apparatus. Referring to FIG. 2, the washing device 20 includes an arm, and nozzles 21, 22, 23, 24, 25 mounted to the arm to spray deionized water 30 onto the polishing pad 14. A slurry dispenser 40, which supplies slurry 32 onto the polishing pad 22, is also mounted to the arm of the washing device 20. The outlet 34 of the slurry dispenser 40 is located at the end of the arm of the washing device 20.
Other conventional slurry dispensers, similar to that described above, are known. For example, a slurry dispenser disclosed in U.S. Pat. No. 5,928,062, issued to Miller et al., includes several slurry outlets through which the slurry flows. The several slurry outlets each are in the form of a nozzle or a hole. The nozzles function to spray the slurry, whereas the holes function to drip the slurry. Another slurry dispenser, disclosed in Japanese Patent Laid-open No. Hei 5-343375, is mounted on the polishing pad itself.
In any case, during the polishing operation, the washing device 20 sprays deionized water 30 through the nozzles 21, 22, 23, 24, 25 and onto the polishing pad 14 to remove particles and slurry from the polishing pad 14. Specifically, the sprayed deionized water 30 flows from polishing pad 14 carrying the remaining particles and slurry with it and hence, the particles and slurry are removed. In addition to removing particles and slurry during the polishing operation, the washing device 20 serves to clean the polishing pad 14 by supplying deionized water 30 onto the polishing pad 14 after the polishing of substrate has been completed.
FIG. 3 is a cross-sectional view of the washing device 20 shown in FIG. 2. Referring to FIG. 3, the deionized water 30 sprayed onto the polishing pad 14 rebounds from the surface of polishing pad 14 due to the pressure under which the deionized water 30 is sprayed. Moreover, the slurry 30a remaining on the polishing pad 14 also flies off of the polishing pad 14 together with the deionized water. The slurry 30a adheres to the washing device 20 itself and to other components of the polishing apparatus, whereupon the slurry 30a accumulates on the washing device 20 and on other components of the polishing apparatus. Such slurry 30a causes a defect to occur on a substrate during the polishing process. That is, it is difficult to clean the slurry, especially from the components of the polishing apparatus. Eventually, clumped particles of the slurry begin to continuously fall from the components of the polishing apparatus onto the surface of the polishing pad 14. There, the slurry particles scratch the surface of the substrate during the polishing process.
In a short, the slurry entrained by the deionized water rebounding from the polishing pad is a constant source of defects during the polishing process. These defects, which occur on the substrates, decrease the reliability of the semiconductor devices manufactured therefrom.